FAA Powerplant Written Practice Test

In a Jabiru light sport aircraft engine, what drives the integral alternator?

1. The propeller shaft

2. A gear driven by the camshaft

3. A flywheel driven by the crankshaft

4. The engine's oil pump

The correct answer is: A flywheel driven by the crankshaft

The integral alternator in a Jabiru light sport aircraft engine is driven by a flywheel that is connected to the crankshaft. This design allows the alternator to efficiently generate electrical power as the engine runs. The flywheel’s inertial mass helps in stabilizing the engine’s power delivery while also facilitating the alternator's operation by ensuring a consistent rotational speed. The integration of the alternator with the engine is an efficient use of space and mechanical energy. It ensures that electrical power is generated directly from the engine's primary motion, thereby reducing the need for additional drive belts or systems. This arrangement is common in many light sport aircraft engines, where weight and space are critical considerations. In contrast, other options like the propeller shaft or a gear driven by the camshaft do not adequately align with how the Jabiru’s system is designed, as they would either complicate the design or not provide the necessary rotational characteristics for efficient alternator performance. The oil pump is typically responsible for lubrication, which is a separate function from power generation.